Homopolymers, copolymers (including those formed from three or more monomers) and polymer blends of polyvinylidene fluoride (“PVDF”) enjoy wide use in a variety of different applications including the high purity semiconductor industry, the pulp and paper industry, nuclear waste processing industry, general chemical processing industry, food and pharmaceutical processing industry, and so forth.
In a particularly interesting application, high molecular weight polyvinylidene fluoride homopolymers blended with one or more additional resins are used in liquid coating formulations to provide colored coatings to various architectural substrates such as metal siding and roofing, storefront extrusions, curtain walls, louvers, skylights and other miscellaneous metal trim and extrusions. Typically, such liquid coating formulations are factory applied to a properly cleaned, pretreated and primed metal substrate and then oven baked. Typical substrates include aluminum, hot dip galvanized steel, G90 steel (galvanized steel produced by hot dipping to ASTM A653), and 55% aluminum zinc alloy coated steel.
Although such colored coatings exhibit excellent abrasion and weather resistance, they still wear out over time. As a result, attempts have been made to overcoat these products with conventional aqueous polymer dispersion-based paints and/or other roofing products. Unfortunately, such products adhere rather poorly to the PVDF substrate, even if primed with acids or organic solvents.